Support Constants in Enum Cases

[ethereumdegen]

This is my shader file:

let TEXTURE_KIND_REGULAR:i32 = 0;
let TEXTURE_KIND_WARP:i32 = 1;
let TEXTURE_KIND_SKY:i32 = 2; 
.....

@fragment
fn main_fs(vertex: VertexOutput) -> FragmentOutput {
   
    var result: FragmentOutput;

       switch (push_constants.texture_kind) {
        case TEXTURE_KIND_REGULAR:
.....

That throws this error:

 case TEXTURE_KIND_REGULAR:
    │              ^^^^^^^^^^^^^^^^^^^^ expected unsigned/signed integer literal


    expected unsigned/signed integer literal, found 'TEXTURE_KIND_REGULAR'

Now.. i could be doing something wrong here but this is VERY confusing and there are not any good docs i can find about this.

my 'let' vars should work for a switch case --- no ?

[ethereumdegen]

is there a better way to define an immutable constant ?

[cwfitzgerald]

Right now this isn't possible because we haven't implemented const yet, which is how you would implement this in upstream wgsl. If you want this to work that, you need to put literals right on the cases. A preprocessor could help with that.

[cwfitzgerald]

Dependent on #97

[armansito]

Supporting this would be a huge quality of life improvement. In vello, we have to keep multiple files in sync as we can't reference const declarations in switch statements.